JPH10120958A - Aqueous pigment ink composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition excellent in delivery stability and delivery response as an ink for ink-jet recording capable of being smoothly written when used in a writing tool, proving a clear image in high concentration, containing a specific oxidized carbon black in an aqueous medium. SOLUTION: This composition contains preferably 2-20wt.% based on the total of the composition of an oxidized carbon black obtained by oxidizing a carbon black having <=40nm primary particle diameter and >=60mL/100g DBP oil absorption with hypochlorous acid and/or its salt in an aqueous medium. Preferably, the oxidized carbon black is obtained by finely dispersing the carbon black into water and then oxidizing with sodium hypochlorite or simultaneously dispersing and oxidizing. The oxidized carbon black has preferably 100-200nm particle diameters. An acidic group of the oxidized carbon black is preferably neutralized beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink composition and, more particularly, to an aqueous pigment ink composition containing, as a colorant, oxidized carbon black having improved water dispersibility.

[0002]

2. Description of the Related Art Conventionally, aqueous dye ink compositions containing a black dye have been mainly used as recording liquids for writing instruments and ink jet printers. In recent years, an aqueous pigment ink composition using a pigment such as carbon black to impart light resistance and water resistance to a recorded image has attracted attention.

For this type of pigment ink composition, various brands of carbon black which are commercially available as colorants (for color) are used. Among them, acidic carbon black has relatively good affinity for water as compared with neutral or basic ones, and is used for aqueous pigment ink compositions and the like. It is considered that acidic carbon black has an acidic group such as a carboxyl group on its surface. These are generally gas or liquid phase oxidation methods using conventional oxidizing agents such as ozone, nitric acid, hydrogen peroxide, and nitrogen oxides, or surface modification methods such as plasma treatment, such as furnace black. It is obtained by appropriately oxidizing carbon black for color.

[0004] Such a conventional acidic carbon black,
Alternatively, channel black exhibits a certain degree of hydrophilicity, but has insufficient affinity for an aqueous medium and dispersion stability, and is difficult to disperse alone in water. Therefore, when these are used as a coloring agent of an aqueous pigment ink composition, the aqueous medium is prepared by using a dispersing machine in the presence of a so-called pigment dispersant such as various water-soluble synthetic polymers and a surfactant. dispersion,
Need to stabilize.

For example, JP-A-64-6074, JP-A-4-14928
No. 6 describes an aqueous pigment ink composition containing acidic carbon black, a dispersant (anionic surfactant or polymer dispersant) and a buffer. Also, JP-A-3-2103
No. 73 describes an ink-jet ink composition containing an acidic carbon black having a volatile content of 3.5 to 8% by weight and a water-soluble resin. Further, JP-A-3-34073 describes an inkjet recording liquid containing a neutral or basic carbon black and a water-soluble resin.

In general, ink compositions for ink jet recording do not cause clogging of ink discharge nozzles, have good discharge stability, have good storage stability, have high print density, do not generate print unevenness, Excellent dyeing and water resistance,
It is required to have various characteristics such as.

However, when a commercially available carbon black is used as in a conventional aqueous pigment ink composition, the resin forming the dispersant adheres to the orifice or the like and is not redissolved or redispersed. Non-discharge of liquid droplets is likely to occur. In addition, since the aqueous pigment ink composition containing a dispersant has a viscous tone, when performing continuous ejection and high-speed printing for a long time, resistance occurs in the path to the nozzle tip, and ejection becomes unstable, and smooth recording is difficult. Become. In order to solve these disadvantages, the present inventors disclosed an aqueous pigment ink composition containing no pigment dispersant in Japanese Patent Application No. 8-98436. However, in the aqueous pigment ink composition described herein, carbon black exists in the aqueous pigment ink composition in a state of being finely dispersed in fine particles having a particle diameter of 300 nm or less. Generally, carbon black as a colorant becomes redder as the particle size decreases, and there is a problem that the density of the recorded matter does not sufficiently increase even if the carbon black density is increased. For this reason, it is difficult for the conventional aqueous pigment ink composition to sufficiently increase the density of the recorded matter. In addition, they have disadvantages such as easy printing unevenness as compared with the dye ink composition and shading of the printing.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide ink jet recording in which recording is performed by applying vibration or heat energy to a recording liquid to generate droplets. Water-based pigments that have excellent ejection stability and ejection responsiveness when used in, and can be used to write smoothly from a thin pen tip even when used in stationery supplies such as writing implements, and also provide high-density and clear character images. An object of the present invention is to provide an ink composition.

[0009]

According to the present invention, carbon black having a primary particle diameter of 40 nm or less and a DBP oil absorption of 60 ml / 100 g or more is prepared by using a hypohalous acid and / or a salt thereof in an aqueous liquid medium. The present invention provides an aqueous pigment ink composition containing oxidized carbon black obtained by wet oxidation.

Further, the aqueous pigment ink composition of the present invention comprises
Primary particle diameter 40nm or less and DBP oil absorption 60ml / 1
Finely dispersing carbon black having at least 00 g in water; and
And / or oxidizing using a salt thereof.

The carbon black powder used in the present invention is an aggregate of many independent carbon black particles. Each of the independent carbon black particles is an aggregate of finer carbon black particles fixed together. In general, carbon black particles of the smallest dimension that are fixed to each other are called primary particles, and mutually independent carbon blacks formed by aggregating a plurality of primary particles are called secondary particles. In the present specification, the term “primary particle size” means an average particle size of primary particles of carbon black. In contrast, the term “particle size” simply means the average particle size of the secondary particles of the finely dispersed carbon black.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The oxidized carbon black contained in the aqueous pigment ink composition of the present invention is a reaction product obtained by wet oxidizing carbon black with hypohalous acid and / or a salt thereof. .

[0013] Carbon black, which is a raw material of oxidized carbon black, is generally a carbon powder obtained by thermally decomposing or incompletely burning natural gas or liquid hydrocarbons (such as heavy oil and tar). These include channel black, furnace black, lamp black; acidic carbon black, neutral carbon black, basic carbon black;
CI Pigment Black 6, 7 and CI Pigment Black 10;

The carbon black as a raw material used in the present invention has a primary particle size of 40 nm or less, preferably 30 nm or less,
More preferably, it has 30 to 10 nm. If the primary particle diameter is 40 nm or more, the original carbon black itself has low coloring power, and the optical density (reflection density) of the recorded matter is reduced.

The raw material carbon black has a DBP oil absorption of 60 ml / 100 g or more, preferably 100 ml / 100 g or more, more preferably 100 to 200 ml / 10 g.
Has 0g. If the DBP oil absorption is less than 60 ml / 100 g, the transparency of the recorded matter is increased, and the optical density is reduced.

Here, the DBP oil absorption means an amount of a certain amount of dried carbon black to absorb oil such as dibutyl phthalate, and the measuring method is specified in JIS K6221. Details of the measurement method are described in Carbon Black Handbook, edited by Carbon Black Association, published by Tosho Publishing Co., Ltd., pp. 440-441. The DBP oil absorption of a specific product is shown in a catalog or the like issued by each manufacturer.

Specifically, for example, # 3 manufactured by Mitsubishi Chemical Corporation
050, # 3150, # 3250, # 2600, # 23
50, # 2300, # 990, # 980, # 970, #
960, # 950, # 850, # 750, # 650, M
A600, MA100, MA100R, OIL30B,
OIL31B, MA7, MA11, # 55, # 52, #
50, # 47, # 44, # 40, # 33, # 32, # 3
0, # 25, # 20B, # 4000; Toka Black # 3885, # 3855, # 86 manufactured by Tokai Carbon Co., Ltd.
00, # 8500, # 8300, # 8200, # 7700, # 7450, # 7400, # 735
0, # 4550, # L400F, Seast 9, 9
H, 7H, 6, 600, 5H, KH, 3
H, NH, 3, 3M, N, 300, 116
HM, 116; color black FW1, manufactured by Degussa
FW2, FW200, S160, S170, PRINTEX 95, 90, 85, 80, 75,
55, 45, 40, P, 60, L6, L, 300, 30, 30 OP, 3 and 3 O
P, 35; Monarch 1400, 1 by Cabot
300, 1100, 1000, 900, 88
0, 800, 700, Vulcan XC72R, P
9A32, Mogal L, Legal 660R, 500
R, 400R, 330R, 300R, 99R,
Black Pearls 570, 520, 490, 48
0, 470, 460, 450, 430, 42
0, 410, 280, Elftex 115, 5, 8, and 12; Raven 7000, 5750, 5250, 5000 Ultra 2, 3500, 2500 Ultra, and 200 manufactured by Columbian Carbon Co., Ltd.
0, 1500, 1255, 1250, 120
0, 1190 Ultra, 1170, 1080 Ultra, 1040, 1035, 1020, 100
0, 890H, 850, 790 Ultra, 78
0 Ultra, 825, OIL beads, C Ultra
Conductex 975 Ultra, SC Ultra; and the like.

In the present invention, such a raw material carbon black is wet-oxidized in water using hypohalous acid and / or a salt thereof. Specific examples of the hypohalous acid and / or its salt include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite is particularly preferred from the viewpoint of reactivity.

In the oxidation reaction, carbon black and a hypohalite (eg, sodium hypochlorite) are charged into an appropriate amount of water, and the reaction is carried out at 50 ° C. for 5 hours or more, preferably for about 10 to 15 hours.
As mentioned above, it is preferably carried out by stirring at 95 to 105 ° C. At that time, it is preferable that the carbon black is oxidized in a finely dispersed state.

In the present specification, "fine dispersion" refers to secondary particles of carbon black used as a raw material (particle diameter of several tens μm to
(Several μm) in water is referred to as pulverization to a degree close to primary particles. The particle size of the finely dispersed carbon black is 300 nm or less.

The particle diameter of the finely dispersed carbon black in the aqueous pigment ink composition of the present invention is preferably from 75 to 300 nm, particularly preferably from 100 to 200 nm. If the particle size of the carbon black is 75 nm or less, the recorded matter becomes transparent and a sufficient optical density cannot be obtained. On the other hand, when the thickness exceeds 300 nm, sedimentation of carbon black tends to occur.

In general, fine dispersion is performed by an operation of wet grinding in an aqueous medium for 3 to 10 hours using a mill medium and a grinding apparatus. As a mill medium, glass beads, zirconia beads, magnetic beads and the like are used. Ball mill,
Attritors, Fouro jet mixers, impeller mills, colloidal mills, sand mills (eg, bead mills, sand gliders, super mills, agitator mills, Dyno mills (trade name)) and the like.

However, depending on the type of carbon black used as a raw material, it may be finely dispersed only by high-speed stirring using a homogenizer (homomixer) or the like in an aqueous solvent.

The fine dispersion is not necessarily performed before the oxidation treatment. The fine dispersion treatment may be performed simultaneously with the oxidation treatment by stirring or pulverizing in an aqueous solvent such as hypohalite.

The amount of the hypohalite used depends on the type thereof, but is generally from 1.5 to 150% by weight, preferably from 4 to 75% by weight, based on the weight of the carbon black.
% By weight.

The resulting oxidized carbon black is at least about 3% by weight, preferably at least about 5% by weight, more preferably
It has an oxygen content of 10% by weight or more. As a result of the oxidation treatment according to the method of the present invention, the oxygen content increases to about several times to several tens times the oxygen content of the carbon black before the treatment.

The measurement of the oxygen content of the oxidized carbon black is performed by an "inert gas-infrared ray absorption method". In this method, carbon oxide black is heated in a stream of an inert gas such as helium, oxygen is extracted as carbon monoxide, and the amount is measured by an infrared absorption method. For details, see JIS
Z 2613-1976.

The feature of the aqueous pigment ink composition of the present invention is not limited to the oxygen content of the oxidized carbon black contained therein. Although the reason is not clear, the oxidized carbon black in the present invention has an oxygen content of 3 to 10% by weight.
Even so, a stable aqueous dispersion is formed as compared with commercially available carbon black.

Generally, in the reaction between carbon black and hypohalite, various functional groups present on the surface of carbon black are oxidized to form acidic groups such as carboxyl groups, hydroxyl groups, carbonyl groups, and the like. It is said. Many of these polar groups have active hydrogen, and the amount of this active hydrogen can be measured, for example, by the Tweil method.

The oxidized carbon black used in the aqueous pigment ink composition of the present invention preferably has a high surface active hydrogen content (mmol / g). This is because such oxidized carbon black exhibits particularly good water dispersibility. Surface active hydrogen content of the oxidized carbon black contained in the aqueous pigment ink composition of the present invention is not particularly limited,
It is preferably at least about 0.3 mmol / g, more preferably at least about 1.0 mmol / g.

In general, carbon black having a high surface active hydrogen content has many hydroxyl groups and carboxyl groups having active hydrogen on its surface, so that the carbon black itself has improved hydrophilicity. At the same time, the surface area is increased, and it is considered that the water dispersibility is improved as if the surface had chemical properties such as an acid dye.

The feature of the aqueous pigment ink composition of the present invention is not limited to the surface active hydrogen content of the oxidized carbon black contained therein. That is, not all carbon blacks having an active hydrogen content of about 0.1 to about 1.0 mmol / g achieve the object of the present invention.

Next, the oxidized carbon black dispersion after oxidation is filtered (when hot), the obtained wet cake is redispersed in water, and then beads and coarse particles are removed using a mesh wire mesh. Alternatively, after removing the beads and coarse particles, the wet cake may be washed with water to remove by-product salts. Alternatively, the slurry from which beads and coarse particles have been removed may be diluted with a large amount of water, and the membrane may be purified and concentrated as it is.

If necessary, the wet cake of oxidized carbon black is preferably dispersed again in water and subjected to an acid treatment using a mineral acid (for example, hydrochloric acid or sulfuric acid). In the acid treatment, it is preferable that hydrochloric acid is added to the aqueous dispersion to adjust the pH to 3 or less, and the mixture is heated and stirred at 80 ° C. or more for 1 to 5 hours. This is because the acid treatment is advantageous for ammonium chloride or amine salification with aqueous ammonia or an amine compound in the next step. Thereafter, the dispersion is filtered, washed with water, and the obtained wet cake is dispersed in water.

If necessary, the dispersion of oxidized carbon black is then neutralized with a basic compound, preferably an amine compound. Since acidic groups are present on the surface of the oxidized carbon black, at least a part thereof is ionically bonded to a basic compound to form, for example, an ammonium salt, an alkyl ammonium salt, an alkanol ammonium salt, an alkyl alkanol ammonium salt or an alkali metal salt. I do. Thus, by neutralizing the acidic groups of the oxidized carbon black, metal corrosion and nozzle clogging are prevented, and the dispersion stability of the aqueous pigment ink composition and the dyeing of the recorded matter when recorded on paper And water resistance are improved.

Preferred amine compounds include water-soluble and volatile amines and alkanolamines.
Specifically, ammonia, an alkylamine substituted with an alkyl group having 1 to 3 carbon atoms (eg, methylamine, trimethylamine, diethylamine, propylamine); an alkanolamine substituted with an alkanol group having 1 to 3 carbon atoms (eg, , Ethanolamine, diethanolamine, triethanolamine); alkylalkanolamines substituted with an alkyl group having 1 to 3 carbon atoms and an alkanol group having 1 to 3 carbon atoms. A particularly preferred amine compound is ammonia. However, it is not necessary to neutralize all acidic groups into ammonium salts or the like.

These can be used in combination of two or more.
Further, in order to adjust the affinity and dispersion stability for an aqueous medium, and to prevent metal corrosion, some acidic groups on the surface of the oxidized carbon black may be converted into alkali metal salts. Sodium oxide, potassium hydroxide, lithium hydroxide and the like are used in combination with the amine compound.

Thereafter, the dispersion of the neutralized oxidized carbon black is purified and concentrated using a separation membrane having a pore size of 10 nm or less, such as a reverse osmosis membrane or an ultrafiltration membrane. Here, the “refining” means an operation of removing a by-product salt, a polymeric aromatic hydrocarbon (oil component), unreacted carbon black and coarse particles in the raw material carbon black from the oxidized carbon black dispersion as a reaction product, Alternatively, it means an operation of performing an acid treatment. The concentration is generally performed so that the pigment dispersion is a concentrated pigment dispersion having a carbon black content of about 10 to 30% by weight based on water. The pigment dispersion thus obtained can be used as it is as an aqueous pigment ink composition. In this case, the concentration of carbon black is preferably adjusted to 1 to 20% by weight.

The concentrated pigment dispersion may be further dried to obtain a powdery pigment, or may be further concentrated to obtain a pigment dispersion having a pigment concentration of about 50% by weight. Thereafter, these are dispersed in an aqueous medium described below, or a water-soluble resin or a surfactant is added to adjust the concentration to an appropriate value, thereby obtaining the aqueous pigment ink composition of the present invention.

The oxidized carbon black according to the present invention is generally contained in the range of 0.5 to 20% by weight, preferably 2 to 20% by weight, based on the total amount of the aqueous pigment ink composition. If the content of carbon black is less than 0.5% by weight, the printing or writing density becomes insufficient, and if it exceeds 20% by weight, the viscosity of the ink becomes high, the fluidity is difficult to be obtained, and the ejection stability and ejection responsiveness deteriorate. Because.

The aqueous pigment ink composition of the present invention may contain a water-miscible organic solvent, if necessary. In addition, water,
The water-miscible organic solvents and mixtures thereof are referred to herein as
It is called an aqueous medium.

As the water-miscible organic solvent, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, s
C1-C4 alkyl alcohols such as ec-butyl alcohol and isobutyl alcohol; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran (THF) and dioxane; ethylene glycol, propylene glycol, diethylene glycol And polyalkylene glycols such as polyethylene glycol and polypropylene glycol; polyhydric alcohols such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether and triethylene glycol monoethyl ether. Lower alkyl ether; polyethylene glycol monomethyl ether acete Lower alkyl ether acetates such as preparative; glycerol; and 2-pyrrolidone, 2-methylpyrrolidone, pyrrolidone such as N- methyl-2-pyrrolidone. The use amount of these organic solvents is not particularly limited, but is generally in the range of 3 to 50% by weight.

The water-based pigment ink composition of the present invention may contain a water-soluble resin, a surfactant and the like, if desired. This is to improve the dyeing property and water resistance of the recorded matter recorded with the aqueous pigment ink. However, these water-soluble resins and surfactants, unlike pigment dispersants generally used, do not require much performance for dispersing pigments. This is because the oxidized carbon black itself has good dispersibility and redispersibility in an aqueous medium.

As the water-soluble resin which can be preferably used, an acrylic copolymer having an average molecular weight in the range of 50,000 to thousands and an acid value of 150 to 250, and an average molecular weight in the range of 50,000 to thousands And cationic resins.

Examples of the water-soluble acrylic copolymer include:
Acrylic acid- (meth) acrylic acid alkyl ester copolymer, methacrylic acid- (meth) acrylic acid alkyl ester copolymer, (meth) acrylic acid-maleic acid half ester copolymer, (meth) acrylic acid-maleic acid Dialkyl ester copolymer, maleic acid- (meth) acrylic acid alkyl ester copolymer, itaconic acid- (meth) acrylic acid alkyl ester copolymer, methacrylic acid- (meth) acrylic acid 2-hydroxyethyl copolymer, Methacrylic acid- (meth) acrylic acid diethylene glycol copolymer, methacrylic acid- (meth) acrylic acid glycidyl copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid- (meth) Acrylic acid alkyl ester copolymer, styrene-maleic acid- Meth) acrylic acid alkyl ester copolymer, and the like.

Examples of the water-soluble cationic resin include those represented by the formula

[0047]

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A polyallylamine represented by the formula:

[0049]

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A polyvinylamine represented by the formula:

[0051]

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A polyethyleneimine represented by the formula:

[0053]

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Polyvinylpyrrolidone represented by the formula:

[0055]

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A polyamidine (hydrochloride) represented by the formula:

[0057]

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A polyamine sulfone represented by the formula:

[0059]

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And the like.
m and n are positive integers).

Surfactants which can be suitably used include those of the formula

[0062]

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Wherein R ¹ is an alkyl group having 8 to 18 carbon atoms, R ² and R ³ are a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and X is acetic acid or methyl sulfate. Organic acids or inorganic acids such as hydrochloric acid and sulfuric acid];

[0064]

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Wherein R ¹ , R ² and R ³ have 1 to 18 carbon atoms
R ⁴ is an alkyl group having 1 to 18 carbon atoms, a phenyl group or a benzyl group, and X is Cl, Br
Or a quaternary ammonium salt of the formula:

[0066]

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Wherein R is an alkyl group having 1 to 18 carbon atoms, and X is Cl, Br or I.

[0068]

Embedded image

Wherein R ¹ is hydrogen or an alkyl group having 1 to 18 carbon atoms, R ² and R ³ are an alkyl group having 1 to 18 carbon atoms, a hydroxyethyl group or a phenyl group;
X is Cl, Br or I].

These water-soluble resins or water-soluble cationic surfactants are used in an amount of 0.1 to 10% by weight based on the total amount of the aqueous pigment ink composition of the present invention, or the carbon oxide contained in the aqueous pigment ink composition of the present invention. For the weight of black,
It is preferable to add about 0.1 to 1 times the amount.

Further, the water-based pigment ink composition of the present invention may further comprise a viscosity modifier commonly used in this type of ink composition.
Additives such as a fungicide and a rust inhibitor can be appropriately selected and used in an appropriate amount.

Since the aqueous pigment ink composition of the present invention is sufficiently desalted and purified, corrosion of writing instruments and ink jet printers does not occur. Further, since some of the acidic groups on the surface of the carbon black are ammonium salts or the like, there is no need to particularly adjust the pH. Further, a part of the acidic group may be an alkali metal salt derived from an alkali metal (Na, K) salt of hypohalous acid.

According to the present invention, an aqueous pigment ink composition containing oxidized carbon black having a very high degree of oxidation and being excellent in water dispersibility as compared with a commercially available (acidic) carbon black as a colorant. Is provided.

The recorded matter recorded with the aqueous pigment ink composition of the present invention has a high density. For example, when the non-sized paper is immersed in the aqueous pigment ink composition of the present invention for 10 seconds,
The optical density (reflection density) of the colored non-size paper is 1.30 or more. This is because, according to the method of the present invention, by using the above-mentioned specific raw material carbon black, the oxidation reaction is performed uniformly, and at the same time, the activation of the surface of the obtained oxidized carbon black is promoted. This is presumably because the fine dispersion stability is further improved, and the dyeing property and density on non-size paper and plain paper are improved. In the present specification, “non-size paper” means paper that has not been treated (sized) with a sizing agent, and is, for example, bonsai paper.

The aqueous pigment ink composition of the present invention has excellent long-term dispersion stability without adding a pigment-dispersing resin or a surfactant, or without a mechanical dispersion treatment, and is an oxidized pigment. The carbon black does not settle.

The aqueous pigment ink composition of the present invention can be used as various inks for ink jet recording, writing implements, printing, stamping and the like. In particular, the aqueous pigment ink composition of the present invention has good recording / writing characteristics and can perform high-speed printing without printing unevenness even when used as a recording ink composition for recording by an ink jet method or a water-based ballpoint pen. In addition, even when the shorthand is written, the characters do not fade.

Furthermore, the robustness (light fastness and water fastness) of characters and figures recorded on plain paper is excellent, and even when immersed again in water, the carbon black does not flow out and has good dyeing properties, It is excellent in light resistance without discoloration unlike a dye ink composition even when exposed.

Further, since carbon black can be contained at a high concentration, the density of printed matter is excellent, and an optical density equal to or higher than that of a water-soluble black dye is provided.

[0079]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 Commercially available carbon black “MA-100” (primary particle size 2
2 nm, DBP oil absorption 101 ml / 100 g, manufactured by Mitsubishi Chemical Corporation) 300 g was well mixed and finely dispersed in 1000 ml of water, and 450 g of sodium hypochlorite (effective chlorine concentration 12%) was added dropwise to the mixture. Stirred at 105105 ° C. for 10 hours. The obtained slurry was filtered with Toyo Filter Paper No. 2 (manufactured by Advantis) and washed with water until pigment particles leaked. This pigment wet cake is redispersed in 3000 ml of water, and the conductivity is 0.2 mS.
The resultant was desalted with a reverse osmosis membrane, and further concentrated to a pigment concentration of 10% by weight to obtain a pigment dispersion.

The obtained pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-size paper ("Silver 8.25" manufactured by Toyo Shoji Co., Ltd.)
Was immersed for 10 seconds and dried for 2 days. Macbeth densitometer TR
The optical density (OD value) of the colored non-size paper measured using -927 (manufactured by Colmorgen) was 1.45.

Next, an aqueous pigment ink composition having a pigment concentration shown in Table 1 was prepared using the obtained pigment dispersion, and the OD value was measured in the same manner as described above.

[Table 1] Pigment concentration OD value 1% by weight 1.35 2% by weight 1.45 3% by weight 1.47 5% by weight 1.49 10% by weight 1.52

Further, the particle size of the oxidized carbon black contained in the aqueous pigment ink composition was measured using a laser light diffusion type particle size distribution analyzer (trade name: LPA30, manufactured by Otsuka Electronics Co., Ltd.).
00/3100) was 150 nm.

The obtained pigment dispersion is further concentrated,
After drying and pulverization, a fine powder of oxidized carbon black was obtained. When the oxygen content of the obtained oxidized carbon black was measured by "inert gas-infrared ray absorption method", it was 8% by weight. This measurement was performed under the following analysis conditions.

TABLE 2 Analysis instrument: HERAEUS CHN-O RAPIO full automatic elemental analyzer sample decomposition furnace temperature: 1140 ° C. fractionating tube Temperature: 1140 ° C. Using _{gas: N 2 / H 2 = 95} % / 5% of mixed gas flow rate : 70 ml / min Detector: Non-dispersive spectrometer (Binos)

Example 2 Commercially available carbon black "Color Black S-160"
(Primary particle diameter 20nm, DBP oil absorption 150ml / 100
g, manufactured by Degussa Co., Ltd.) 300 g was mixed well with 1000 ml of water, and then added to sodium hypochlorite (effective chlorine concentration 12%) 45
0 g was added dropwise, and the mixture was stirred at 100 to 105 ° C for 10 hours. To this solution, 100 g of sodium hypochlorite (effective chlorine concentration: 12%) was further added, and the mixture was dispersed for 3 hours by a horizontal dispersing machine filled with beads. The resulting slurry was diluted 10-fold with water, adjusted to pH 2 with hydrochloric acid, desalted with a reverse osmosis membrane to an electric conductivity of 0.2 mS, and further adjusted to pH 10 by adding monoethanolamine. It was concentrated to a concentration of 20% by weight to obtain a pigment dispersion.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.42.

In the same manner as in Example 1, the particle size and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 3 shows the measurement results.

Example 3 Commercially available carbon black “# 20B” (primary particle size: 40 n
m, DBP oil absorption 115ml / 100g, manufactured by Mitsubishi Chemical Corporation) 250g was well mixed and finely dispersed in 1000ml of water, and then 400g of sodium hypochlorite (effective chlorine concentration 12%) was added dropwise. Stirred at ~ 104 ° C for 20 hours. The resulting slurry was filtered through Toyo Filter Paper No. 2 (Advantis),
Washing was performed until the pigment particles leaked. The pigment wet cake was redispersed in 10 liters of water, desalted with a reverse osmosis membrane until the electric conductivity was 0.2 mS, and further concentrated to a pigment concentration of 10% by weight to obtain a pigment dispersion.

The obtained pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.35.

In the same manner as in Example 1, the particle size and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 3 shows the measurement results.

Example 4 500 g of commercially available carbon black "Raven 1040" (primary particle diameter 28 nm, DBP oil absorption 100 ml / 100 g, manufactured by Columbian Carbon Co., Ltd.) was mixed well with 1500 ml of water, and then mixed with Sodium chlorate (effective chlorine concentration 12
%) Was added dropwise and the mixture was stirred at 100 to 105 ° C for 5 hours. 500 g of sodium hypochlorite (effective chlorine concentration 12%)
Was added and dispersed for 3 hours with a horizontal disperser filled with beads. Dilute the resulting slurry 10-fold with water and p with hydrochloric acid
Adjusted to H2, desalted with reverse osmosis membrane until conductivity 0.2mS,
Further, the pH was adjusted to 10 by adding 25% aqueous ammonia, and then concentrated to a pigment concentration of 20% by weight to obtain a pigment dispersion.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.36.

In the same manner as in Example 1, the particle size and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 3 shows the measurement results.

Example 5 Commercially available carbon black “Color Black FW1” (1
A primary particle size of 13 nm, DBP oil absorption of 170 ml / 100 g, manufactured by Degussa Co., Ltd.) 500 g was well mixed and finely dispersed in 2000 ml of water, and then sodium hypochlorite (effective chlorine concentration: 12%) was added thereto.
800 g was added dropwise, and the mixture was stirred at 100 to 105 ° C for 10 hours. The obtained slurry was filtered with Toyo Filter Paper No. 2 (manufactured by Advantis), and washed with water until pigment particles leaked. This pigment wet cake was redispersed in 10 liters of water, desalted with a reverse osmosis membrane until the electric conductivity was 0.2 mS, and further concentrated to a pigment concentration of 10% by weight to obtain a pigment dispersion.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.32.

In the same manner as in Example 1, the particle diameter and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 3 shows the measurement results.

[0096]

[Table 3] Raw material carbon black Example of oxidized carbon black pH Primary particle diameter DBP oil absorption Oxygen content Particle diameter Optical density (nm) (ml / 100g) (%) (nm) (OD value) 1 3.5 22 101 About 8 150 1.45 2 4.5 20 150 About 10 110 1.42 3 8.0 40 115 About 5 253 1.35 4 2.8 28 100 About 12 128 1.36 5 4.5 13 170 About 11 103 1.32

Example 6 First, 30 g of the 10% pigment dispersion obtained in Example 1, 5 g of ethanol, 5 g of 2-methylpyrrolidone, 50 g of water and Joncryl J501 (a styrene-maleic acid-modified acrylic resin manufactured by Johnson Polymer Co., Ltd.) Acid value 205, average molecular weight 12,000) 2
An aqueous pigment ink composition was prepared by mixing 10 g of a 9.5% aqueous solution (neutralizing ammonia water).

Next, this ink composition was set on an ink jet recording apparatus (trade name: HG5130 (manufactured by Epson Corporation)) and printed on plain paper. Ink ejection is stable,
Immediately printed. The printed matter was glossy, the pigment did not flow even when immersed in water after drying, and the dyeability and water resistance were good. The nozzle used was for a general aqueous dye ink, but the ink did not solidify, and there was no ejection failure in a printing test several hours later. Also,
Even if this ink was stored at 50 ° C. for one month, there was no ejection failure. Further, even if this ink was stored at 50 ° C. for one month, no sediment was generated, and the particle diameter and viscosity did not change. Even when the printing test was performed again, the ejection of the ink was stable, and printing could be performed smoothly. The reflection density of the solid printed portion was measured using a Macbeth densitometer TR-927 (manufactured by Colmorgen) to find that it was 1.48.
Was satisfactory.

Example 7 First, 15 g of the 20% pigment dispersion obtained in Example 4, 5 g of ethanol, 5 g of 2-methylpyrrolidone, 65 g of water and PAA-L
(Polyarylamine manufactured by Nitto Boseki Co., Ltd. (average molecular weight of about 1
An aqueous pigment ink composition was prepared by mixing 10 g of a 20% aqueous solution (10,000).

When the obtained ink composition was evaluated in the same manner as in Example 6, good results were obtained as in Example 6.

Comparative Example 1 Carbon black "Special Black 250" (primary particle diameter 56 nm, DBP oil absorption 46 ml / 100 g) manufactured by Degussa Co., Ltd. was used in place of carbon black "MA-100" manufactured by Mitsubishi Chemical Corporation. A 10% pigment dispersion was obtained in the same manner as in Example 1 except for the above.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.25.

In the same manner as in Example 1, the particle size and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 4 shows the measurement results.

Comparative Example 2 Carbon black "Color Black S-1" manufactured by Degussa Corporation
60 ”instead of carbon black“ M ”manufactured by Mitsubishi Chemical Corporation.
A-8 "(primary particle diameter 24 nm, DBP oil absorption 58 ml
/ 100 g), except that 2 g
A 0% pigment dispersion was obtained.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.23.

In the same manner as in Example 1, the particle size and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 4 shows the measurement results.

Comparative Example 3 Except that carbon black “# 900” (primary particle diameter 16 nm, DBP oil absorption 56 ml / 100 g) manufactured by Mitsubishi Chemical Corporation was used instead of carbon black “# 20B” manufactured by Mitsubishi Chemical Corporation. In the same manner as in Example 3, a 10% pigment dispersion was obtained.

The resulting pigment dispersion was diluted with water to a pigment concentration of 2% by weight to prepare an aqueous pigment ink composition. Non-sized paper was immersed in this ink composition for 10 seconds and dried for 2 days. The optical density (OD value) of the colored non-size paper measured in the same manner as in Example 1 was 1.20.

In the same manner as in Example 1, the particle diameter and oxygen content of the oxidized carbon black contained in the aqueous pigment ink composition were measured. Table 4 shows the measurement results.

[0110]

[Table 4] Raw material carbon black Comparative example of oxidized carbon black pH Primary particle size DBP oil absorption Oxygen content Particle size Optical density (nm) (ml / 100g) (%) (nm) (OD value) 1 3.1 56 46 About 6 142 1.25 2 3.5 24 58 Approx. 10 51 1.23 3 8.0 16 56 ~ 55 Approx. 6 36 1.20

[0111]

As described above, even with a low-concentration aqueous pigment ink composition, a sufficient print density and a clear character image without print unevenness can be obtained. In addition, even with a high-concentration aqueous pigment ink composition, resistance in the path to the recording head is low, ejection stability is good, ink redispersibility is excellent, and long-time printing and high-speed printing can be performed. Further, the recorded matter is excellent in water resistance and light resistance.

Claims (6)

[Claims] 1. Oxidation obtained by wet oxidation of carbon black having a primary particle size of 40 nm or less and a DBP oil absorption of 60 ml / 100 g or more with an aqueous liquid medium using hypohalous acid and / or a salt thereof. An aqueous pigment ink composition containing carbon black. 2. A part of the acidic group formed on the surface of the oxidized carbon black is composed of ammonia, alkylamine,
The aqueous pigment ink composition according to claim 1, wherein the aqueous pigment ink composition is neutralized with at least one basic compound selected from the group consisting of alkanolamines and alkali metal hydroxides. 3. The particle size of the oxidized carbon black is 75.
The aqueous pigment ink composition according to claim 1, which has a thickness of from 300 to 300 nm. 4. The aqueous pigment ink composition according to claim 1, wherein the content of the oxidized carbon black is 0.5 to 20% by weight based on the total amount of the aqueous pigment ink composition. 5. The non-sized paper colored by immersion in the aqueous pigment ink composition for 10 seconds has an optical density of 1.
The aqueous pigment ink composition according to claim 1, which has 30 or more. 6. A primary particle diameter of 40 nm or less and a DBP oil absorption of 60.
Finely dispersing carbon black having milliliters / 100 g or more in water; and oxidizing the carbon black with hypohalous acid and / or a salt thereof;
A method for producing an aqueous pigment ink composition comprising: